HARD ROCK – CRUSH IT OR LET IT BREAK ITSELF?

BRIAN PUTLAND & REBECCA SCIBERRAS

ABSTRACT

Many ore bodies are getting harder, more abrasive, and lower in grade. One of the issues designers face is minimizing capital and operating costs when treating such ores. Designers often look to secondary or tertiary crushing followed by grinding in a semi-autogenous grinding mill with recycle crusher followed by a ball mill (SABC) or ball mill only circuit when treating extreme ores (Axb<30, BWi >18 and Ai>0.5). This approach is capital intensive and for abrasive ores often results in a circuit with high maintenance and operating costs.

This paper looks at how these extreme ores can also be treated successfully using primary crushing and single stage semi-autogenous or autogenous grinding (S/AG) milling. Benchmarking of this style of circuit is provided with detailed case studies of the design and operation of single stage SAG milling circuit with recycle crushing (SAC) at the Mt. Carlton Au/Cu/Ag and Mako Au projects. Discussed are why these circuits were successful and the challenges encountered.

Lastly, the learnings from these circuits are used to explore the part that autogenous grinding circuits may play in future comminution circuits.

Keywords


SAG, ramp up, design, commissioning, comminution circuit selection, competent ore, single stage.

Categories

0